Digital audio/video receivers such as Internet Protocol (IP) digital audio/video receivers (IPTV) are becoming increasingly popular. Unfortunately, channel change times with such receivers are relatively high. One potential cause for such high channel change times in the digital audio/video domain involves the relative complexity of digital audio/video receivers which is ever increasing due new distinguishing features such as time-shift recording of live digital video streams, handling of multicasted or unicasted video streams that are encoded with highly complex video encoding techniques, handling of video stream descrambling and application of error correction methods. With the increasing complexity of digital audio/video receivers many resources must be managed inside such receivers, such as network controllers, hard disks, reception buffers, error correctors, video and audio stream decoders.
Channel changing for an digital audio/video receiver can thus be a rather complex and resource-demanding process: stop of transmission of the current video/audio stream must be requested, internal hard- and/or software resources must be freed, reception of a next video/audio stream must be requested, and internal resources must be set up for the reception of the next video/audio stream; upon reception of the desired video/audio stream video/audio data must be buffered, possibly error correction is applied, possibly data is descrambled, video/audio data must be synchronized, decoded and finally, rendered. Channel change delay is caused by all or some of these operations. In digital audio/video receivers equipped with a time-shift feature based on a hard disk, time-shift offers the possibility to “pause” a live transmission, the channel change delay will be even longer when time-shifting is used, due to relatively slow disk access. As a result of all of these steps, channel change times can become relatively long, which may be unacceptable to users, and thus for digital audio/video providers.
Prior art document US2006075428 describes caching video packets for a most likely next channel in a buffer in a receiver in anticipation of a television subscriber changing channels. These prior art solutions focus on providing decodable I-frames for a next channel as soon as possible in order to reduce the blank period when switching channels. However, prior art techniques are rather complex to implement and have drawbacks of increasing the complexity and thereby the costs of transmitters and receivers.
Accordingly, there is a need for a technique that allows reducing the time necessary to effectuate a channel change operation in digital audio/video receivers in a simple way.